1. Field of the Invention
The present invention relates to a method of manufacturing an integrated light-weight solid metal shaft and an integrated light weight-weight metal pipe shaft for use in a business machine,and an integrated light weight solid metal shaft and a similar pipe shaft manufactured by the same method.
2. Description of the Prior Art
A drive shaft for reciprocally mounting a print head and a paper feed roller of a business machine are generally constructed as a solid metal shaft.
It has been proposed to use a metal pipe shaft in such a drive shaft and a paper feed roller in order to decrease weight or to save material.
The conventional pipe shaft having a small thickness for a drive shaft of a print head and a carriage is weak in strength and the printing pressure of the printer causes disarrangement and resonance of the pipe drive shaft, causing mutilation of the printed letters and characters.
When a thin pipe shaft is used for a paper feed roller, it is difficult to mount coaxially each end bearing portion of the pipe shaft with an outer periphery of an inner shaft, thus causing vibration of the drive pipe shaft and also backlash between the gears and the drive pipe shaft during rotation thereof. When the press-fitted portion of the drive pipe shaft is strengthened, it has a large volume and becomes unsuitable for a drive shaft.